Cell Cycle Flashcards
What is the function of cell division
Grow and repair damage
In short, what is the cell cycle
A mother cell divides in to two daughters cells
What are the four phases of the cell cycle
M-phase
G1-phase
S-phase
G2-phase
What is the G0-phase
When the cell does not take part in the cell cycle
In what phase does the cell enter the cell cycle
G1
What happens in the S-phase
DNA Will be duplicated
(S > synthesis)
What happens in the G2-phase
The cell prepares itself for division
What happens in the M-phase
The division take place
(M > mitosis)
What happens in the G1-phase
The cell grows
What is the first check point of the cells cycle
Is the environment suitable for the division
What is the second check point off the cell cycle
Was the DNA properly duplicated
Is the environment still good
What is the third check point
Are all the chromosomes attached to the spindle
In what phase are the checkpoints of the cell cycle
1: end of G1
2: beginning M
3: mid M (between metaphase and anaphase)
What proteins regulate the checkpoints
Cyclins and cyclin-dependent kinase (Cdks)
How is Cdk activated
(Cyclin kinase)
Phosphorylation
How is Cdk inactivated
(Cyclin kinase)
Phosphorylation in two places
How is Cyclin regulated
By protein production and breakdown
How is Cyclin deactivated
By attaching to a ubiquitin flag
It wil than be broken down
What types of Cyclins are there
G1/S- Cdk
S-Cdk
M-Cdk
What happens with the Cyclins during mid M-phase
They are all broken down
What is the first step of activation of G1-Cdk
Mitogen attaches on a receptor
What wil the receptor, with mitogen attached to it, activate
Ras protein
How will MAP kinase activate G1-Cdk
Immediate early gene expression > gene regulatory protein > delayed-response gene expression > G1-Cdk
What will G1-Cdk phosphorylate
Rb protein, it becomes active
What happens if Rb protein is activated
It will let go of E2F protein
What does E2F protein do
Triggers S-phase gene transcription
What proteins are being produced by S-phase gene transcription
G1/S-Cyclin
(Cyclin E)
S-Cyclin
(Cyclin A)
On what have the g1/S and S Cyclin positive feedback
E2F protein
What proteins divides DNA in two strands
Helicase
On what does ORC (origin recognition complex) bind
Origins in the DNA (in the G1 phase)
Which two proteins does ORC recruit
Cdc6
helicase
What do Cdc6 and Helicase create
Prereplicative complex (pre-RC)
Why can’t Helicase open the DNA in the G1 phase
Because it’s bound to Cdc6
What does S-Cdk to Cdc6
It phosphates it so it loses binding to Helicase
How are more copies of the DNA prevented
ORC will stay bound and phosphorylated
What happens if there is a problem with the cell cycle or with apoptose
(Disbalans)
Tumors
What is a risk factor for tumors
P53
How is p53 activated
Damaged DNA > AMT/ATR kinase activation > Chk1/2 kinase activation > phosphorylation of p53 ( loses Mdm2) > active p53 > makes RNA of p21
What does p21 to
P21 mRNA activates translation of Cdk inhibitor proteins (p21) which deactivated G1/S-Cdk
Why is a mutation in P53 bad
Bad cell (with damaged DNA) will enter the cell cycle
What is an other risk factor for the cell cycle
DNA viruses
What does a DNA virus do
Name 2
Produces E7 (looks like E2F) > binds to Rb > the real E2F does not get inactive but keeps working
Produces E6 > binds to p53 > so on
What determines the speed of the cell cycle
Regulation of Cyclin/Cdk activity
